"The startling truth is that animals farmed for meat and dairy are now one of the greatestthreats to the planet.

"The United Nations last year issued a shocking report on the environmental damage being done by livestock. I became a vegetarian for health reasons. Then I found out about the awful animal abuse in factory farms and dairy herds and became a vegan.

"The easiest and most effective way of cutting our contribution is to change our diet and go vegan. It is that simple."

Heather - who is currently involved in a bitter divorce battle with estranged husband Sir Paul McCartney - currently appears in two adverts for Vegetarians International Voice for Animals (Viva!) to encourage people to embrace a plant-based diet to save the world from global warming.

Heather's first ad' features the line: "Hey Meaty, you're making me so hot!"

The former glamour model - who lost her left leg below the knee in a motorbike accident in 1993 - appears in a second advert which plays on her disability, warning meat-eaters: "You haven't got a leg to stand on!"

Viva! claim vegetarianism can halt the globe's rising temperatures, which they claim are the result of the methane created by flatulent livestock.